The disturbance of sleep, in the form of repetitive, stereotypical anxiety dreams, occurs commonly in posttraumatic stress disorder (PTSD). In polysomnographic studies of PTSD, we have identified abnormalities of tonic and phasic rapid eye movement (REM) sleep as a possible biologic substrate. Two types of phasic events, rapid eye movements and leg muscle twitch bursts, occurred more frequently in PTSD subjects compared to age-matched normal control subjects. These two measures remained elevated on a subsequent night of recording, suggesting that heightened REMS phasic event generation might be an essential property of sleep in PTSD. The major confounders of these polysomnographic data have been the history of alcohol abuse and the co-diagnosis of major depression in many of the PTSD subjects. Defining the relative contributions of the PTSD diagnosis, past alcohol abuse, and major depression to heightened REMS phasic event generation in PTSD is the problem to be investigated in this proposal. This hypothesis will be tested by recording over three nights the polysomnograms of a group of Vietnam combat veterans with PTSD and a control group, a matched subset of whom will have a history of alcoholism.